#include <stdio.h>
int main()
{
    long long a = 2, b = 1, t;
    int n;
    double sum = 0;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        if(i > 12){
            sum += 1.618034;
            continue;
        }
        sum += (double)a / b;
        t = a;
        a += b;
        b = t;
    }
    printf("%.2f", sum);
    return 0;
}